Novel water-soluble polyurethane nanomicelles for cancer chemotherapy: physicochemical characterization and cellular activities

The amphiphilic polyurethane was prepared through formation of urethane bounds between hydroxyl groups in poly (tetramethylene ether) glycol (PTMEG) and dimethylol propionic acid with isocyanate groups in toluene diisocyanate (TDI). The free isocyanate groups were blocked with phenol, while the free carboxyl groups of dimethylol propionic acid were reacted with triethylamine to attain ionic centers in the polymer backbone. These hydrophobic PTMEG blocks displayed self-assembly forming polymeric nanomicelles in water. The PTX loaded PU nanomicelles showed suitable physical stability, negative zeta potential charge (-43) and high loading efficiency (80%) with low level of critical micelle concentration (CMC). In vitro drug release profile showed a faster rate of drug liberation at pH 5.4 as compared to that of pH 7.4, implying involvement of a pH-sensitive mechanism for drug release from the nanomicelles. The kinetic of release exquisitely obeyed the Higuchi model, confirming involvement of diffusion and somewhat erosion at pH 5.4. These nanomicelles significantly inhibited the growth and proliferation of the human breast cancer MCF-7 cells, leading them to apoptosis. The real time RT-PCR analysis confirmed the activation of apoptosis as result of liberation of cytochrome c in the cells treated with the PTX loaded PU nanomicelles. The comet assay analysis showed somewhat DNA fragmentation in the treated cells.Based upon these findings, we propose that the bioactive waterborne polyurethane nanomicelles can be used as an effective nanocarrier for delivery of anticancer chemotherapies such as paclitaxel.Paclitaxel is an anticancer drug that has successfully been used against a variety of tumors such as ovarian and breast cancers [1]. It is a lipophilic agent with limited solubility in water (0.3 μg/ml) [2], thus the most available injectable formulation of paclitaxel (i.e., Taxol？) has been formulated using mixture of Cremophor EL and ethanol (1:1 v/v). However, such for